When I studied CQC we would fight over rubber guns a couple of things I noticed.
-A trained person could usually get out of the line of fire and strip a gun from an untrained person, if their was an opportunity.
-A trained gun holder could most always keep a person in the line of fire.
-A group could strip a gun from a trained person but the gun will probably be empty by the time they get it. The best thing a group could do is try to keep the gun low under chest cavities.
This was in rubber gun play land, so take it with a grain of salt.